Scratch strain recorder

ABSTRACT

A scratch strain gauge has an annular target guided into its recording position where it cooperates with a scratch element on a scratch arm to indicate strains of opposite senses. The gauge has a guide adjacent one edge of a plate on which rollers are mounted for rotatably mounting the target in cooperation with brushes. The guide cooperates with a groove in the periphery of the target to insure that the groove receives one of the rollers, then the brushes, and finally the other roller as the target is inserted into its recording position. Ears, which are disposed above the rollers and extend outwardly beyond the rollers to overlie portions of the target when the target is in its recording position, aid in insuring that the target is seated on the roller tongues when disposed in its recording position.

- United States WEE? [1 1 Prewitt et al.

[54] SCRATCH STRAIN RECORDER 22 Filed: June 28,1971 21 Appl.No.: 157,187

[52] U.S. Cl. ...346/77, 346/124, 346/137 [51] Int. Cl. ..G01d 115/02[58] Field of Search ..346/7, 77 R, 124, 137;

[56] References Cited UNITED STATES PATENTS Prewitt et al ....73/88 R2/1969 Prewitt et al. ..346/7 51 Apr.3,1973

Primary Exa miner.loseph W. l-lartary AttorneyFrank C. Leach, Jr.

[57] ABSTRACT scratch element on a scratch arm to indicate strains ofopposite senses. The gauge has a guide adjacent one edge of a plate onwhich rollers are mounted for rotatably mounting the target incooperation with brushes. The guide cooperates with a groove in theperiphery of the target to insure that the groove receives one of therollers, then the brushes, and finally the other roller as the target isinserted into its recording position. Ears, which are disposed above therollers and extend outwardly beyond the rollers to overlie portions ofthe target when the target is in its recording position, aid in insuringthat the target is seated on the roller tongues when disposed in itsrecording position.

14 Claims, 4 Drawing Figures PATENTEDAPR3 1975 INVENTORS RICHARD H.PREWITT ERICH A. SCHMIDT VOLKER SCHMlDT ATTORNEY SCRATCH STRAIN RECORDERIn U.S. Pat. No. 3,430,250 to Richard H. Prewitt et al, there is shown ascratch strain recorder or gauge in which the target is rotatablymounted on a pair of rollers and two brushes and is rotated in only onedirection is response to strains of one sense of a work to which thegauge is attached at two spaced areas. Strains in each sense arerecorded on the target by a scratch arm, which is mounted on a platesecured to a different area of work than a plate supporting the rollers.

Under certain conditions, difficulty is sometimes encountered ininserting the target so that a groove in the periphery of the targetreceives the wires of the two brushes and the rollers to rotatably mountthe target. This problem is usually encountered when the gauge ismounted in a relatively inaccessible position so that the user cannotsee the relationship of the target groove, roller, and brush wiresduring the insertion of the target into its recording position.

Therefore, when inserting the target, it is necessary for the groove toreceive the rollers, a first group of wires, which form a brush toprevent rotation of the target in one direction, and a second group ofwires, which form a brush to cause rotation of the target in theopposite direction in response to strains of one sense on the work. Ifthese wires fail to enter the groove, the tar-' get may not rotate asdesired even though the rollers are disposed in the groove.

Additionally, if the target is not properly positioned in its recordingposition so that the wires are unable to enter the groove of the target,the possibility exists that the wires may become separated from eachother and damaged sufficiently. As a result, the first group of wireswill not engage the base of the groove to prevent rotation of the targetin one direction and can create excessive friction because of theirfriction against the periphery of the target, and the second group maynot have sufficient force to advance the target in the oppositedirection when thework is subjected to strains in one sense due to thereduced number of wires engaging the base of the groove and theadditional drag from the displaced wires at the periphery of the target.

The scratch strain gauge of the present invention is an improvement ofthe scratch strain gauge of the aforesaid Prewitt et al patent bysatisfactorily solving the foregoing problems whenever they occur. Thepresent invention enables one to insert the target into its recordingposition without having to visibly view whether the groove of the targetis disposed in a plane so as to receive the rollers. The presentinvention also satisfactorily solves the problem of the wiresinadvertently not entering the groove in the target since the presentinvention insures that the groove in the target is positioned in a planeto initially receive one of the rollers and a target groove guidewhereby it is positioned to receive the wires as the target is advancedto its recording position since the wires are in the same plane as therollers and the target groove guide. The present invention also permitsthe replacement of the target in a cold climate where it is necessary towear heavy gloves.

When the scratch strain gauge of the aforesaid Prewitt et al patent isdisposed in an inaccessible position insofar as the user being able toview the position of the target, it is possible for the user to insertthe target with sufficient force that he would displace the targetbeyond its recording position. To prevent this from occurring, thepresent invention employs a stop for preventing the target from beingadvanced beyond the recording position during insertion of the target.

Under some conditions such as when used on an aircraft, for example, thetarget of the scratch strain gauge of the aforesaid Prewitt et al patentmay vibrate when in its recording position because of the vibrations ofthe work to which the gauge is attached. The present inventionsatisfactorily solves this problem by providing means to preventvibration of the target when the target is disposed in its recordingposition.

When inserting the target into its recording position in the scratchstrain gauge of the aforesaid Prewitt et al patent, the possibilityexists that the scratch arms pointed element, which engages the uppersurface of the target to form the scratches thereon, will scratch theupper surface of the target during insertion of the target into itsrecording position. Furthermore, the pointed element of the scratch armmay be damaged when it comes against the outer upper surface of thetarget during insertion of the target into its recording position.Accordingly, the present invention has a unique arrangement forpreventing the pointed element of the scratch arm from engaging theupper surface of the target during insertion of the target into itsrecording position.

- With the present invention, the group of wires, which rotate thetarget when the work is subjected to strains of one sense, could beinadvertently withdrawn from a support, which holds the wires closetogether adjacent the target and is integral with the target grooveguide, prior to mounting the gauge on the work, since the support is onone plate and the wires are connected to the other plate. The two platesof the scratch strain gauge are movable relative to each other untilmounted on two spaced areas of the work that has strains which it isdesired to record. The present invention prevents this from occurring byhaving means to limit the amount of relative longitudinal movementbetween the two plates when they are not attached to two spaced areas ofthe work. Accordingly, the group of wires, which rotate the target inresponse to strains of one sense on the work, cannot easily be removedto a position in which they would not be supported by the support.However, if desired, the two plates can be separated by rotating theplate, which has the rotating group of wires connected thereto, whilemoving the two plates relative to each other so that the limit means arerendered ineffective.

An object of this invention is to provide an improved scratch strainrecorder.

Another object of this invention is to provide a scratch strain recorderin which the target is always properly inserted into its recordingposition.

A further object of this invention is to provide a scratch strainrecorder'in which the target does not vibrate.

Still another object of this invention is to provide a scratch strainrecorder in which the target is not scratched by the scratch meansduring insertion of the target to its recording position or removal ofthe target from its recording position.

A still further object of this invention is to permit target insertionwithout having to manually lift the scratch arm. r

Other objects of this invention will be readily perceived from thefollowing description, claims, and drawing.

This invention relates to an improvement in a recording instrumentcomprising first and second support means with scratch means mounted onthe first support means. A target, which records motions in oppositesenses by scratches formed on the target due to movement of the scratchmeans, is rotatably mounted on the second support means. The target hasa groove formed in its periphery with one of the opposite walls of thegroove being engaged by rotatably mounted means, which are supported onthe second support means, to rotatably support the target. The firstsupport means has means connected thereto to engage the base of thegroove to rotate the target, which is removably mounted on the rotatablymounted means, in response to motions in one of the senses only. Theimprovement includes means supported on the second support means andcooperating with the target during insertion of the target into itsrecording position to dispose the groove of the target to receive therotatably mounted means and the base engaging means.

The attached drawing illustrates a preferred embodiment of theinvention, in which:

FIG. 1 is a top plan view of the scratch strain recorder of the presentinvention;

FIG. 2 is a fragmentary plan view of a portion of the recorder of FIG. 1with the target partially inserted;

FIG. 3 is a side elevational view of a portion of the scratch strainrecorder of FIG. 1; and

FIG. 4 is a side elevational view of a guide utilized with the gauge ofFIG. 1.

Referring to the drawing and particularly FIG; 1, there is shown ascratch strain gauge of the present invention having an elongated baseplate and an end base'plate 11, which is spaced from the base plate 10.Each of the base plates 10 and 11 is relatively thin and may be formedof any suitable material.

The base plate 10 has a lip 12 on its end, which is remote from the endbase plate 11. The lip 12 is adapted to be secured to an area of a workor part that is to have its :strains recorded by the scratch straingauge of the present invention in the manner more particularly shown anddescribed in the aforesaid Prewitt et al patent. The end base plate 11is adapted to be secured to a second area of the same work or part inthe manner more particularly shown and described in the aforesaidPrewitt et al patent. The two areas are longitudinally spaced from eachother.

The elongated base plate 10 supports an annular member 16, whichfunctions as the target of the scratch strain gauge of the presentinvention. The annular member 16- has a continuous groove 17 formed inits periphery to receive a pair. of rollers 18, which are rotatablymounted on the base plate 10 adjacent opposite edges thereof.

Each of the rollers 18 has an enlarged central portion 19 (see FIG. 3),which abuts against one of opposite side walls 20 and 21 of the groove17 in the annular I member 16. The periphery of the annular member 16has an upper portion 22, which is above the groove 17, engaging an uppercircular portion 23 of each of the rollers 18. The periphery of theannular member 16 also has a lower portion 24, which is below the groove17, bearing against a lower circular portion 25 of each of the rollers18.

The rollers 18 are mounted with respect to the annular member 16 so thatthe enlarged central portion 19 of the roller 18 does not extend intothe groove 17 to engage its base or bottom 26. Thus, friction betweenthe rollers 18 and the annular member 16 is reduced to permit easierrotation of the annular member 16. Furthermore, the engagement betweenthe circular portions 23 and 25 of each of the rollers 18 and theportions 22 and 24 of the periphery of the annular member 16 minimizesany friction on the upper or lower surface of the annular member 16 dueto mounting thereof. Accordingly, the rotatable mounting of the annularmember 16 by the rollers 18 is a substantially friction-free mounting.

Each of the rollers 18 is rotatably mounted on a shaft 27, which has itslower end fixed to the base plate 10. The upper end of each of theshafts 27 is fixed to an ear 28, which is formed by bending a portion ofthe base plate 10 adjacent the lip 12.

The annular member 16 is held against clockwise (as viewed in FIG. 1)rotation by a retaining or holding means. The retaining or holding meanscomprises one or more relatively thin members or elements 29, which areadapted to engage against the base or bottom 26 of the groove 17. Themembers 29 may be formed of any suitable material as long as the edges,which engage the bottom or base 26 of the groove 17 in the annularmember 16, are sharp. As an example, the member 29 could be a wireformed of metal and have its end ground or could be formed of glassfiber and have its end broken to provide the sharp edge.

The members 29 pass through a tubular member 30, which is secured to thebase plate 10, and are secured to a tubular member 31 intermediate theends of the members 29. The members 29 also extend through a tubularmember 32, which also is supported by the base plate 10.

If the members 29 are metal wires, they could be secured to the tubularmember 31 by soldering or.

crimping, for example. If the members 29 are glass fiber, they could besecured to the tubular member 31 by a suitable adhesive or crimping, forexample. The tubular members 30 and 32 are fixed to the upper surface ofthe base plate 10 by suitable means such as soldering or welding, forexample.

The scratch means for forming the scratches on the upper surface of theannular member 16, which is the target, includes an am 33 having one endfixed to the end base plate 1 l. The arm 33 has a pointed element 34 atits end, which is remote from the end base plate 11, for forming thescratches on the upper surface of the annular member 16. The pointedelement 34 extends downwardly from the lower surface of the arm 33,which overlies the annular member 16, and is urged downwardly againstthe annular member 16 due to the flexing force of the arm 33. g

Accordingly, each time that there is relative motion between the areasof the work, there is relative motion between the base plate 10 and theend base plate 11 so as to cause the pointed element 34 to form ascratch on the upper surface of the annular member 16. It should 34 mustbe capable of scratching the upper surface of the annular member 16.Furthermore, if the base plate l0 and the arm 33 are made of materialshaving the same rate of thermal expansion, they will not adverselyaffect final results when auxiliary plates of the same material as thatof. the structure being recorded are added underneath the plates and 11and attached thereto at the adjacent edges of the two plates 10 and Theannular member 16 is rotated in a counterclockwise direction by adriving means. The driving means includes a plurality of relative thinmembers or elements 35, which have their edges sharpened to engage thebottom or base 26 of the groove 17 in the same manner as the members 29.The embers 35 are preferably formed of the same material as the members29. It should be understood that the members 29 and 35 are of a hardermaterial than the annular member 16 so that the edges of the members 29and 35 bite into the bottom or base 26 of the groove 17 in the mannermore particularly shown in the aforesaid Prewitt et al member31.

The members 35 extend through a curved tubular member 37, which is fixedto the upper surface of the base plate 10 by suitable means such aswelding or soldering, for example. The ends of the members 35 extendthrough an opening 38 (see FIGS. 1 and 4) in a support 39. The support39 includes a U-shaped member 40, which has one leg secured to the baseplate 10 and its other leg held in spaced relation by a spacer 41 (seeFIG. 4). The spacer 41 cooperates with a guide element 42 on the support39 to form the opening 38 and has the members 35 bear thereagainst.

As a result, the 'members 35 are guided, in cooperation with the tubularmember 37, so that they are retained in positive engagement withthe baseor bottom 26 of the groove 17. The tubular member 37 serves to hold themembers 35 in a close relation to each other while the edge of thespacer 41 insures that the members 35 have positive engagement with thebase or bottom 26 of the groove 17. This insures that the annular member16 rotates counterclockwise (as viewed in FIG. 1) during each movementof the end base plate 1 1 toward the base plate 10.

As shown in FIGS. 3 and 4, the guide element 42 has a protruding portion43, which extends beyond the U- shaped member 40 and is thinner than thegroove 17 in the annular member 16. The portion 43, which is slightlythicker than the remainder of the guide element 42, is disposed in thesame plane as the enlarged central portion l9'of each of the rollers 18.

Each of the ears 28 extends beyond the enlarged central portion 19 ofthe rollers 18 as shown in FIG. 1. Each of the ears 28 has a sufficientlength to overlie a portion of the annular member 16 when the annular 7member 16 is in its recording position as shown in FIG. 1.

As shown in FIG. 3, the bottom surfaces of the ears 28 are so disposedwith respect to the enlarged central portion 19 of each of the rollers18 that the annular member 16 cannot be inserted between the roller 18and the portion 43 of the guide element 42 without the groove 17 of theannular member 16 receiving the enlarged central portion. 19 of theroller 18 and the portion 43 of the guide element 42.

Accordingly, the portion 43 of the guide element 42 insures that theannular member 16 is raised sufficiently with respect to the base plate10 so that the groove 17 of the annular member 16 can receive theenlarged central portion 19 of the roller 18, which is adjacent the edgeof the base plate 10 over which the annular member 16 is passed in beinginserted into its recording position. At the same time, the ear 28insures that the annular member 16 cannot be disposed so high that thegroove 17 of the annular member 16 will not receive the enlarged centralportion 19 of the roller 18. Thus, the present invention insures thatthe annular member 16 cannot be inserted too high or too low withrespect to the rollers 18 whereby the annular member 16 is disposed inits recording position and is rotatably mounted.

Because of the portion 43 of the guide element 42 raising the annularmember 16 with respect to the base plate 10, the groove 17 is sopositioned that it could engage the scratch arm 33. Accordingly, thescratch arm 33 has a raised portion or lip 43 for cooperation with theupper surface of the annular member 16 so. that the scratch arm 33 islifted slightly as .the annular member 16 is advanced to its recordingposition. This camming of the scratch arm 33 by the annular member 16prevents the scratch arm 33 from engaging the groove 17 of theannularmember 16.

As the annular member 16 is advanced to its recording position, therelative movement between the annular member 16 and the pointed element34 of the arm 33 could result in scratches appearing on the uppersurface of the annular member 16. This would result in a waste of aportion of the available recording surface of the annular member 16 ormisleading information.

' Accordingly, the arm 33 has a protrusion 44 extending downwardly fromits lower surface for engagement with the upper surface of the annularmember 16 as the. annular member 16 is inserted into its recordingposition. As shown in FIG. 1, the protrusion 44 is supported on the arm33 at a position in which it will not engage the annular member 16 whenthe annular member 16 is in its recording position. Thus, the pointedelement 34 of the arm 33 engages the upper surface of the annular member16 when the annular member '16 is in its recording position.

When the annular member 16 .is inserted into its recording position, theuser could exert a sufficient force on the annular member 16 to push itbeyond its recording position. This would primarily be whenever thescratch strain gauge is mounted in a position in which the user cannotview the scratch strain gauge.

Accordingly, the base plate 10 has a projection 45 extending upwardlytherefrom by bending a portion of the base plate 10 upwardly. Theprojection 45 limits the amount of advancement of the annular member 16.When the annular member 16 is in its recording position, the annularmember 16 is slightly spaced from the projection 45 as shown in FIG. 1.This is accomplished because of the forces of the members 35 and themembers 29 on the annular member 16. These have sufficient resiliency toreturn the annular member 16 to the position of FIG. 1 if the annularmember 16 should be advanced to the position in which it engages theprojection 45 on the base plate 10.

As shown in FIGS. 1 and 4, the members 29 also extend through theopening 38 in the support 39 and bear against an inclined edge of theguide element 42. While the members 29 function to prevent rotation ofthe annular member 16 in a clockwise direction, the members 29 also maybe employed to manually advance the antion 46 extending slightlyupwardly from its upper surface. The projection 46 will not engage thebottom surface of the annular member 16 as long as there is no vibrationof the work since the base plate is sufficiently spaced from the annularmember 16. However, if vibration of the work is transmitted through thebase plate 10, the projection '46 functions to prevent vibrations of theannular member 16. v

The arm 33 has an opening or window 47 (see FIG. 2) through which theuser may view the members 29 and the members 35. This enables one toascertain whetherthe members 29 and 35 are in engagement with theannular member 16.

Since the base plate 10 and the end base plate 11 are movable relativetov each other until they are fixed to spaced areas of the work, the endbase plate 11 could be moved sufficiently relative to the base plate 10so that the members 35 could cease to be disposed within the opening 38.To prevent this, the arm 33 has an upwardly extending projection 48 forcooperation with an ear'49, which is formed by bending theportion of thebase plate 10 at its end adjacent the end base plate 11. When theprojection 48 engages the ear 49, no further longitudinal separation ofthe end base plate 11 from the base plate 10 can readilyoccur. With theprojection 48 engaging the ear 49, the members 35 still extend throughthe opening 38. However, if desired, the end .base plate 11 can beseparated from the base plate 10 by rotating the end base plate 11counterclockwise while separating the two plates 10 and 11.

To insert the annular member 16 into its recording position, theannular'member 16 is advanced beneath the ear 28 so that the groove 17of the annular member With the annular member 16 in the position of FIG.2, the members 29 and 35, which are held in the same plane as theportion 43 of the guide element 42, are disposed in the groove 17 in theannular member 16. Thus, the annular member 16 is positioned to receivethe members 29 and 35 in the groove 17.

As the annular member 16 continues to be advanced from the position ofFIG. 2 to the position of FIG. 1, the lip 43 of the arm 33 and theprotrusion 44 combine to lift the pointed element 34 of the arm 33 sothat it does not engage the upper surface of the annular member 16 asthe annular member 16 progresses to its recording position of FIG. 1.The spring forces of the members 29 and 35.cooperate to act against thebottom or base 26 of the groove 17 to push the annular member 16 to therecording position of FIG. 1. That is, the members 29 and 35 urge theannular member 16 to the position of FIG. 1 in which the other of therollers 18 has the enlarged central portion 19 also disposed within thegroove 17 in the annular member 16.

As previously mentioned, if the user should exert too great a force onthe annular member 16 as it is being inserted, the annular member 16would advance until it engages the projection 45. Upon release of theannular member 16 by the person who is inserting the annular member 16,the forces of the members 29 and 35 in combination with the forcesexerted by the rollers 18 will move the annular member 16 to itsrecording position of FIG. 1.

The annular member 16 is removed from its recording position by movingthe annular member 16 in the opposite direction to that in which it wasinserted. As the annular member 16 is removed, the protrusion 44 on thearm 33 again lifts the pointed element 34 on the arm 33 so thatscratching of the upper surface of the clockwise manually whenever-it isdesired by merely moving the tubularmember 31 until it engages thetubular member 30. This will produce a slight counterclockwise rotationof theannular member 16.

It should be understood that this invention is suitable as a recordingtransducer for recording temperature, acceleration, pressure, and thelike in the same manner as the recorder of the aforesaid Prewitt et alpatent.

An advantage of this invention is that the target can be properlypositioned at its recording position even when the user cannot see thegauge in which the target is to be disposed. Another advantage ofthisjnvention is that there is no inadvertent scratching of therecording surface of the target during insertion of thetarget to its 16receives the portion 43 of the guide element 42 and the enlarged centralportion 19 of the roller 18 over which the ear 28 is positioned. Sincethe portion 43 of I the guide element 42 is spaced from the enlargedcenv groove 17 and lesser than the diameter of the annular member 16,the annular member 16 is easily positioned as shown in FIG. 2.

modifications in the arrangement and construction of A r the partsthereof may be resorted to without departing from the spirit and scopeof the invention.

We claim:

1. A recording instrument comprising first and second support means,scratch means mounted on said first support means, a target forrecording motions in opposite senses by scratches formed on said targetdue to movement of said scratch means, said target being rotatablymounted on said second support means, said target having a groove formedin its periphery, means rotatably mounted on said second support meansand engaging one of the opposite walls of said groove to rotatablysupport said target, means connected to said first support means andengaging the base of said groove to rotate said target in response tomotions in one of the senses only, said target being removably mountedon said rotatably mounted means, the improvement including:

means supported on said second support means and cooperating with saidtarget during insertion of said target into its recording position todispose said groove of said target to receive said rotatably mountedmeans and said base engaging means, and said target cooperating meansbeing disposed to cooperate with said target during insertion of .saidtarget into its recording position and to not cooperate with said targetwhen said target is in its recording position.

2. The improvement according to claim 1 in which said rotatably mountedmeans comprises a pair of rollers rotatably mounted on said secondsupport means, each of said rollers engages one of the opposite walls ofsaid groove to rotatably mount said target, said target in circular,said target cooperating means includes means positioned in substantiallythe same plane as the portion of each of said rollers that engages oneof the opposite walls of said groove, and said positioned means isdisposed from one of said rollers a distance greater than the diameterof said base of said groove and lesser than the diameter of said target.

3. The improvement according to claim 2 including means disposed aboveeach of said rollers to cooperate with said target during its insertioninto its recording position to prevent said groove of said target frombeing positioned above said positioned means.

4. The improvement according to claim 3 in which each of said disposedmeans includes a member extending beyond the periphery of said roller soas to overlie a having a guide disposed in the same plane as saidrollers so that said guide enters said groove when said target isinserted between one of said rollers and said guide for disposition ofsaid target in its recording position, and said guide being disposedfrom said one roller a distance greater than the diameter of said baseof said groove and lesser than the diameter of said target.

6. The improvement according to claim 1 in which said base engagingmeans includes a'plurality of elements; first means cooperating withsaid elements to hold said'elements together; second means, separatefrom said first element cooperating means, cooperating with saidelements to insure that said elements engage the base of said groove;and said first and second element cooperating means being supported onsaid second support means and said second element cooperating meansbeing disposed adjacent said target and closer to said target than saidfirst element cooperating means. I

7. The improvement according to claim 6 in which said second elementcooperating means and said target cooperating means are integral.

8. The improvement according to claim 1 in which said target cooperatingmeans includes means positioned in the same plane as said rotatablymounted means that engages one of 'the opposite walls of said groove.

9. The improvement according to claim 1 including means, separate fromsaid target cooperating means, cooperating with said. target to preventvibration thereof when said target is in its recording position and saidfirst and second support means are secured to spaced areas of a worksusceptible to motions in opposite senses.

10. The improvement according to claim 1 in which said scratch means hasmeans to prevent said scratch means from forming scratches on saidtarget during insertion of said target into its recording position orremoval of said target from its recording position.-

11. The improvement according to claim 1 in which said scratch means hasmeans cooperating with said target to automatically lift said scratchmeans above said target during insertion of said target into its targethaving a groove fonned in its periphery, means rotatably mounted on saidsecond support means and engaging one of the opposite walls of saidgroove to rotatably support said target, means connected to said firstsupport means and engaging the base of said groove to rotate said targetin response to motions in one of the senses only, said target beingremovably mounted on said rotatably mounted means, the improvementincluding:

means cooperating with said target to prevent vibration thereof whensaid target is in its recording position and said first and secondsupport means are secured to spaced areas of a work susceptible tomotions in opposite senses.

13. A recording instrument comprising first and second support means,scratch means mounted on said first support means, a target forrecording motions in opposite senses by scratches formed on said targetdue to movement of said scratch means, said target being rotatablymounted on said second support means, said target having a groove formedin its periphery, means rotatably mounted on said second support meansand engaging one of the opposite walls of said groove to rotatablysupport said target, means connected tosaid first support meansandengaging the base of said groove to rotate said target in response tomotions in one of the senses only, said target being removably mountedon said rotatably mounted means, the imtarget having'a groove formed inits periphery, means rotatably mounted on said second support means andengaging one of the opposite walls of said groove to rotatably supportsaid target, means connected to said first support means and engagingthe base of said groove to rotate said target in response to motions inone of the senses only, said target being removably mounted on saidrotatably mounted means, the improvement including:

said scratch means having means cooperating with said target toautomatically lift said scratch means above said target during insertionof said target into its recording position.

1. A recording instrument comprising first and second support means,scratch means mounted on said first support means, a target forrecording motions in opposite senses by scratches formed on said targetdue to movement of said scratch means, said target being rotatablymounted on said second support means, said target having a groove formedin its periphery, means rotatably mounted on said second support meansand engaging one of the opposite walls of said groove to rotatablysupport said target, means connected to said first support means andengaging the base of said groove to rotate said target in response tomotions in one of the senses only, said target being removably mountedon said rotatably mounted means, the improvement including: meanssupported on said second support means and cooperating with said targetduring insertion of said target into its recording position to disposesaid groove of said target to receive said rotatably mounted means andsaid base engaging means, and said target cooperating means beingdisposed to cooperate with said target during insertion of said targetinto its recording position and to not cooperate with said target whensaid target is in its recording position.
 2. The improvement accordingto claim 1 in which said rotatably mounted means comprises a pair ofrollers rotatably mounted on said second support means, each of saidrollers engages one of the opposite walls of said groove to rotatablymount said target, said target in circular, said target cooperatingmeans includes means positioned in substantially the same plane as theportion of each of said rollers that engages one of the opposite wallsof said groove, and said positioned means is disposed from one of saidrollers a distance greater than the diameter of said base of said grooveand lesser than the diameter of said target.
 3. The improvementaccording to claim 2 including means disposed above each of said rollersto cooperate with said target during its insertion into its recordingposition to prevent said groove of said target from being positionedabove said positioned means.
 4. The improvement according to claim 3 inwhich each of said disposed means includes a member extending beyond theperiphery of said roller so as to overlie a portion of said target whensaid target is in its recording position.
 5. The improvement accordingto claim 1 in which said rotatably mounted means comprises a pair ofrollers rotatably mounted on said second support means, each of saidrollers engages one of the opposite walls of said groove to rotatablymount said target, said target is circular, said target cooperatingmeans includes a member supported on said second support means andhaving a guide disposed in the same plane as said rollers so that saidguide enters said groove when said target is inserted between one ofsaid rollers and said guide for disposition of said target in itsrecording position, and said guide being disposed from said one roller adistance greater than the diameter of said base of said groove andlesser than the diameter of said target.
 6. The improvement according toclaim 1 in which said base engaging means includes a plurality ofelements; first means cooperating with said elements to hold saidelements together; second means, separate from said first elementcooperating means, cooperating with said elements to insure that saidelements engage the base of said groove; and said first and secondelement cooperating means being supported on said second support meansand said second element cooperating means being disposed adjacent saidtarget and closer to said target than said first element cooperatingmeans.
 7. The improvement accorDing to claim 6 in which said secondelement cooperating means and said target cooperating means areintegral.
 8. The improvement according to claim 1 in which said targetcooperating means includes means positioned in the same plane as saidrotatably mounted means that engages one of the opposite walls of saidgroove.
 9. The improvement according to claim 1 including means,separate from said target cooperating means, cooperating with saidtarget to prevent vibration thereof when said target is in its recordingposition and said first and second support means are secured to spacedareas of a work susceptible to motions in opposite senses.
 10. Theimprovement according to claim 1 in which said scratch means has meansto prevent said scratch means from forming scratches on said targetduring insertion of said target into its recording position or removalof said target from its recording position.
 11. The improvementaccording to claim 1 in which said scratch means has means cooperatingwith said target to automatically lift said scratch means above saidtarget during insertion of said target into its recording position. 12.A recording instrument comprising first and second support means,scratch means mounted on said first support means, a target forrecording motions in opposite senses by scratches formed on said targetdue to movement of said scratch means, said target being rotatablymounted on said second support means, said target having a groove formedin its periphery, means rotatably mounted on said second support meansand engaging one of the opposite walls of said groove to rotatablysupport said target, means connected to said first support means andengaging the base of said groove to rotate said target in response tomotions in one of the senses only, said target being removably mountedon said rotatably mounted means, the improvement including: meanscooperating with said target to prevent vibration thereof when saidtarget is in its recording position and said first and second supportmeans are secured to spaced areas of a work susceptible to motions inopposite senses.
 13. A recording instrument comprising first and secondsupport means, scratch means mounted on said first support means, atarget for recording motions in opposite senses by scratches formed onsaid target due to movement of said scratch means, said target beingrotatably mounted on said second support means, said target having agroove formed in its periphery, means rotatably mounted on said secondsupport means and engaging one of the opposite walls of said groove torotatably support said target, means connected to said first supportmeans and engaging the base of said groove to rotate said target inresponse to motions in one of the senses only, said target beingremovably mounted on said rotatably mounted means, the improvementincluding: said scratch means having means to prevent said scratch meansfrom forming scratches on said target during insertion of said targetinto its recording position or removal of said target from its recordingposition.
 14. A recording instrument comprising first and second supportmeans, scratch means mounted on said first support means, a target forrecording motions in opposite senses by scratches formed on said targetdue to movement of said scratch means, said target being rotatablymounted on said second support means, said target having a groove formedin its periphery, means rotatably mounted on said second support meansand engaging one of the opposite walls of said groove to rotatablysupport said target, means connected to said first support means andengaging the base of said groove to rotate said target in response tomotions in one of the senses only, said target being removably mountedon said rotatably mounted means, the improvement including: said scratchmeans having means cooperating with said target to automatically liftsaid scratch means above said target during insertion of said targetinto its recording posItion.